Question

The sum of an A.P. is 525 if its first term is 3 and the last term is 39 then its common difference is

Answer 1

Sn= 525
a = 3
l = 39
therefore, we know that,
Sn = n/2(a+l)
Sn = n/2(3+39)
525 = n/2(42)
n = 25
now,
An = a + (n-1)d
there by putting all the values we get ,
d= 3/2

Answer 2

3/2 is right answer.........